1. Field of the Invention
The present invention relates to an endoscope that uses broadband light and narrow band light for illuminating light.
2. Description of the Related Art
In recent years, endoscopes have been widely used for endoscopy by inserting an insertion portion into a subject.
An inside of the subject is illuminated with broadband illuminating light covering a visible wavelength band, enabling acquisition of an observed image almost equivalent to observation with bare eyes.
Meanwhile, there are proposed endoscopes that illuminate a site to be observed using narrow band illuminating light covering a certain wavelength band only, in addition to broadband illuminating light covering a visible wavelength band, to acquire an observed image (observed image of flow in vessels near a superficial layer) using narrow band light, which is different from a normal observed image, in order to enhance an imaging function of the endoscopes.
For example, a first related art endoscope disclosed in Japanese Patent Application Laid-Open Publication No. 2003-079571 includes a first light-emitting device in a distal end portion of an insertion portion, and light emitted from the first light-emitting device is emitted to the inside of a living body via a first light distribution lens.
Furthermore, it is disclosed that a second light-emitting device is provided in an operation section, and light emitted from the second light-emitting device is guided by a light guide and emitted from a distal end face of the light guide to the inside of a living body via a second light distribution lens.
Furthermore, an endoscope according to a second related art example disclosed in Japanese Patent Application Laid-Open Publication No. 2003-164417 includes a prism, and the prism guides white color light from a white color light source apparatus or ultraviolet light from an excitation light source to a rear end of a light guide provided through an almost entire length of the inside of the endoscope by, e.g., switching between the white color light and the ultraviolet light, and the guided light is emitted from a distal end face of the light guide via a light distribution lens.